1. Field of the Invention
The present invention generally relates to a chip package structure, in particular, to a chip package structure having high voltage protection.
2. Description of Related Art
In the design of a chip package structure in need of high voltage input (for example, a power source module in charge of the power source or an IGBT module for controlling the driving of the motor), in order to meet the safety requirements, such as the UL Standard, and ensure the normal operation of the package structure, the creepage distance and clearance distance between the voltage input end (for example, a lead) and the metal material (for example, a heat dissipation device) of the package structure should be taken into consideration, so as to prevent the conduction between the lead and the heat dissipation device to result in electrical shorts, and prevent a transient high voltage input by the lead from directly shorting to the low voltage end (i.e., the heat dissipation device) to threaten the safety of the user.
FIG. 1 is a cross-sectional view of a conventional chip package structure. Referring to FIG. 1, the conventional chip package structure 100 employs a heat fin 110 in a special shape to increase a clearance distance D1 between the heat fin 110 and leads 120. In particular, the heat fin 110 has a neck portion 112 connected to a molding compound 140, for enlarging the clearance distance D1 between the heat fin 110 and the leads 120. In addition, the molding compound 140 has several grooves 142 on a surface 144 adjacent to the heat fin 110, and the grooves 142 help to increase a creepage distance D2 between the heat fin 110 and the leads 120.
However, the heat fin 110 in a special shape can only be obtained through a particularly designed mold, so the manufacturing cost of the heat fin 110 is very high. Further, during the design of the members (such as bonding wires 150, a chip 160, a substrate 130, and a portion of the leads 120) in the molding compound 140, the positions of the above members should avoid the grooves 142, so as to prevent the members from being exposed by the grooves 142. Thus, the design freedom of the members is quite limited.
In addition, U.S. Pat. No. 5,672,910 provides a flat-shaped insulating sheet covered the heat sink to enlarge the creepage distance and the clearance distance. However, the excessively long flat-shaped insulating sheet may affect the convection of the heat sink and increase the size of the package structure. Moreover, package structures disclosed in U.S. Pat. No. 5,698,899 and Japanese Patent Publication No. 06-061375 and No. 2000-236047 all cannot effectively enlarge the creepage distance and the clearance distance.